It’s lucky the master’s gone to bed (6)
I believe the answer is:
mascot
'it's lucky' is the definition.
(I know that mascot are lucky)
'master's gone to bed' is the wordplay.
I cannot quite understand how this works, but
'master's' could be 'mas' (Master of Arts) and 'mas' is present in the answer.
'bed' could be 'cot' (cot is a type of bed) and 'cot' is found within the answer.
This accounts for all the letters.
This explanation may well be incorrect...
'the' is the link.
Can you help me to learn more?
(Other definitions for mascot that I've seen before include "Character or object used to bring good luck, or represent an organisation" , "'Symbol, for a team say (6)'" , "that's charming?" , "Good-luck item" , "Lucky charm" .)